Objectives: The aim of this study was to evaluate patients’ informedness of antibiotic side effects, the relationship between patients’ informedness of antibiotic side effects and demographic and socioeconomic indicators and the relationship between patients’ informedness of antibiotic side effects and the habit of reading patient information leaflet. Study Design: Cross-sectional study. Participants and Methods: The study included 159 adults of all age groups, regardless of when they took antibiotics last time. Data on the participants was collected on the basis of an online anonymous questionnaire constructed for the purpose of this research. The questionnaire included demographic and socioeconomic indicators of the participants and a number of specific questions whose purpose was to determine the participants’ knowledge on certain concepts about the drugs, the source of information about the drugs, their proper use, possible side effects and contraindications and also the habit of reading the patient information leaflet. Results: The most common source of information about medications were doctors. Participants have shown good knowledge in all answers to questions about the side effects of antibiotics, their contraindications and proper use. No correlation was found between respondents’ awareness of the side effects of antibiotics with age, education and employment status. Women showed greater knowledge of antibiotics in certain matters than men. Subjects who read the drug instructions show greater knowledge than those who do not read them. Conclusion: Participants have shown good informedness about the side effects of antibiotics and their use. No correlation was found between the level of informedness with age, education and employment status. Women showed greater knowledge than men. People who read the drug instructions showed greater knowledge than those who don’t.